Tilting boom



April 30, 1940- c. s. SCHROEDER 'I'ILTING BOOM Filed Sept. 2, 1937 4 Sheets-Sheet l INVENTOR 67/ 09455 6. SCH/905056 BY ATTORNEY April 30, 1940. ,S HREDER T 2,198,793

.TILTING' BOOM Filed Sept. 2, 1937 4 Sheets-Sheet 2 INVENTOR 0/42; as 5 50/20:012

/ffi 1 ATTORN EY April 1940- c. s. SCHROEDER 2,198,793

TILTING BOOM Filed Sept. 2, 1937 4 Sheet s-Sheet 3 'INVENTOR 67/484 5 5. 501/901-0519 BYMQ ATTORNEY A ril 30, 19404 c. s; SCHROEDER TILTING BOOM Filed Sept. 2. 19s 4 Sheets-Sheet 4 M f 2 5% m Mm m MYW M [m ATTORNEY Patented Apr. 30, 1940 UNlTED STATES PATENT OFFICE TILTING BOOM Charles S. Schroeder, Philadelphia, Pa.,

assignor I Application September 2, 1937, sem No. mama 11 Claims.

This invention relates to a tilting boom and means for mounting the said boom. More particularly, my invention relates to the mounting of atilting boom on an industrial truck.

The tilting boom of my invention is of a general type well known in the art. This general type usuallycomprises a very heavy and rugged boom pivoted at one end about a mounting memher, and carrying at its extreme other end a load sheave on which is reeved a load cable. One end of this cable is adapted for actuation by a cable reeling mechanism for moving the cable about the load sheave. The other end of the cable carries a load hook-which is adapted to lower and lift a load when reeved about the load sheave of the boom. The construction is such that when the load is being lifted, once it is moved as far upwardly relatively to the boom as it can be moved relatively to the boom, further reeling in of the cable will movethe boom and load together about the pivot on which the boom is mounted.

In a construction of the class described, it will be readily appreciated that certain forces will be resolved about the load sheave, such forces being dependent on the weight of the boom, the weight of the load, and the pull exerted on the cable. It is absolutely essential that the resultant of these various forces be so related relatively to the pivot about which the boom swings, that the said resultant will be on the side of the said pivot tending to swing the boom downwardly. It will be readily appreciated that should the resultant fall on the other side of the pivot on which the boom is mounted so as to tend to swing the boom upwardly, the boom will move out of control into an extreme upward position, from which position it will be impossible to lower the boom.

0 Those skilled in the art will readily observe that the resultant of the forces indicated, may be properly located by simply determining the relation of the boom pivot to the end of the boom carrying the load sheave, so that the two will be displaced a considerable distance, one relatively to the other. The resultant of the forces exerted by the weight of the boom, and by the load on the sheave, will always be so great as to cause the said resultant to fall on n the side of the boom pivot tending to swing the boom downwardly in every possible position of the boom. This arrangement will naturally prevent a free upwardly swlngingboom at all times, but will result in a high cable stress necessary 5: to overcome the moments of the forces exerted (Ci. 212-7li) by the weight of the load and the weight of the boom.

My invention has for its main object the arrangement of a boom and its mounting, so that the resultant of the forces described will always fall on the side of the boom pivot tending to swing the boom downwardly about its pivot,while at the same time, maintaining quite low the cable stress.

In brief, my invention" contemplated the mounting of the boom so that it may change its pivotal axis as it swings with its load. I prefer, in carrying out my invention, to pivot my boom on a bearing member which is itself 'pivotally mounted relatively to the main body of the industrial truck carrying the boom. In this way, the boom may tilt relatively to its bearing member on one pivot. or together with said bearing member about a second pivot, the pivot of the bearing member. The arrangement is such that just before the resultant of the forces about one pivot is about to resolve itself so as to be on the wrong side of the said pivot to allow a free upward swinging of the boom, the pivot changes so as to re-locate the resultant of the forces on the proper side of the boom pivot. Other features of importance will be referred to when describing my invention in detail, and will be presented in the claims which follow.

Before describing my invention in detail, I shall now describe the drawings in which a preferred embodiment of my invention is shown. In the drawings, Fig. 1 is an elevation of an industrial truck on which is mounted a boom embodying my invention. Figs. 2 and 3 illustrate parts of Fig. 1 in different positions. Fig. 4 is a detail of the boom holding construction for holding the boom in a particular elevated position against the forces tending to swing it downwardly. Figs. 5 and 6 are respectively side and end views of the bearing member about which my boom is pivoted. Fig. 7 is a force diagram illustrating the location of the resultant of the forces of the load and cable relatively to the pivots about which the boom of my invention swings. Fig. 8 is a stress diagram similar to Fig. 7 but illustrating the stresses as they would be developed in a construction in which the boom would be pivoted at a particular point far displaced from the mounting of its load sheave so as to prevent a free upward flying boom. Fig. 9 illustrates the mounting of a boom in a conventional manner without the relatively great displacement of its pivot point, and illustrates how a flying boom would result.

Referringnow more particularly to the drawings, a standard industrial truck is shown in Fig. 1, and is designated by reierence numeral l6. It has the usual operator's platform Ii, control pedals |2, power unit l9, steering wheel i4 and traction control levers l6. Carried on the main frame of the truck is a mast |6 about which rotates a boom carrying member II. This boom carrying member rotates freely about the mast i6 and carries a sector H with which cooperates a pawl l9 controlled by a handle 26 whereby to lock the boom carrying member H in a particular rotated position on the mast II. It will be noted that the handle 26 is always available for manipulation by the operator occupying platform A hearing member 2| (Figs. 5 and 6) is pivoted at 22 on the boom carrying member i1, and is adapted to rotate on the said pivot 22 from the position illustrated in Figs. 1 and 3 to the position illustrated in Fig. 2. The bearing member 2| has a sleeve portion 23 which is bored as at 24 for the mounting of a pivot shaft 26 on which is pivoted the boom 26. Lugs 21 are formed on the bearing member 2| for cooperation with portions of the rear surface of the boom 26 so as to limit the upward pivoting movement of the boom 26 relatively to the bearing member 2|.

- .It is also through the lugs 21; that the boom 26 imparts movement to the bearing member 2| for moving the bearing member integrally with the boom about the pivot shaft 22.

The rotating boom supporting member has a horizontal extension 26 which carries the motor mechanism for reeling a cable 26, the motor mechanism being designated by reference numeral 96, while the power reel is designated by reference numeral 9|. The cable 29 runs over a load sheave 92 carried on the outer end of the m 26, and extends downwardly over the load sheave, andis joined to a load hook 33 which carries a load, in this case designated by reference numeral 94. It will be appreciated that the reeling of the cable 29 acts through the load -hook 39 to move the boom 26 about the two pivots 25 and 22, while swinging the boom upwardly from the position of Fig. 1 to the position of Fig. 2. It is intended that the boom be lowered from the position of Fig. 2 to the positlon of Fig. 1 through its own weight and the weight of the load 34, the cable 29controlling the lowering movement.

For preventing lowering movement of the boom 26, there is employed a ratchet bar 96, best illustrated in Fig. 4, controlled by a pawl 36 which is secured by a screw 31 to a shaft 96 carried by a lever 39 actuated in turn by a control bar 46 pivoted at 4| to a handle 42. The handle 42 is in turn pivoted at 49 to the sleeve 44 in which the ratchet bar 36 slides. A spring 46 urges the pawl 96 into one of a series of notches 4.6 in

the ratchet bar 96. Operation of the handle 42 moves the pawl 36 out of a particular notch 46, and allows the ratchet bar 36 to move together with the boom 26 downwardly under the influence of gravity.

There is a special cooperation between pawl 36 and the notches 46 of ratchet bar 36 to prevent release of the pawl 36 from any of the notches 46 until the cable 29 has been placed under tension by the partial elevation of the boom 26. To accomplish this, each of the notches 46 is undercut for cooperation with the pawl 96, so that it is impossible to move the pawl 96 out of any of the notches 46 until the ratchet bar 36 is actuated somewhat by the tension applied to the cable 29. As soon as this tension is sumoient to relieve the pressure between one of the notches 4'6 and the pawl 36, the pawl 36 may be moved out of holding position by the lever 42. Because of this relation of the parts, it is necessary to apply tension to the cable 29, and thereafter, through the cable 29, control the lowerins oi the load. It will be appreciated that the power lowering mechanism 96, 3| is constructed with the usual brakes, so that through the said brakes, the lowering movement of the load may be controlled. The pawl 36 holds the boom in a particular elevated position when the load is to belowered relatively to the boom, as to the position of Fig. 1, by the reeling out of the cable.

Fig. 1 illustrates the boom in a particular lowered position with the load 94 lowered somewhat away from its extreme upper position. If it now be desired to raise the load and move the boom 26 upwardly, power is applied to the reel 3| by motor 96 and this moves the load book 33 to its uppermost position against the boom 26, thereafter swinging the boom 26 about its pivot shaft 26 on the bearing member 2| until the rear surfaces of the boom 26 contact lugs 21 on the bearing member 2|. This position of the parts is illustrated in Fig. 3.

Thereafter, further reeling in of the cable 29 will cause a tilting of the boom-26 together with bearing member 2| about the pivot shaft 22. During this elevation of the parts. it will of course be appreciated that the pawl 36 is continuously cooperative with successive notches 46 of ratchet bar 96.

Should it be desired to lower the boom and load together, it is merely necessary to apply tension to the cable 29 suillcient to relieve the pressure between the pawl 36 and a particular one of the notches 46, so that the pawl 96 may be withdrawn from looking position by handle 42. Thereafter, the load 34 and boom 36 may be lowered under control of the cable 29, as will be appreciated. If it be desired to lower the load relatively to the boom, the boom is locked by pawl 36 while the cable 29 is allowed to reel outwardly.

In order to fully understand the efleotiveness of my invention, it is necessary to study quite thoroughly the force diagrams of Figs. 7, B and 9. Fig. 7 illustrates two different positions 01 my boom 26 and the position of the resultant of the cable and the load forces relatively thereto. The distances set forth in the force diagrams are millimeters. and are in true proportion to an actual boom mounting. The weight of the boom, for the sake of simplicity, is not considered.

In the lowered position of the boom, illustrated in dotted lines in Fig. 7, the load is shown displaced 86 millimeters from the center of the mast i6. In this position, the load is 78 mm. from pivot 26, while the tension in the cable 29 is 64 mm. from. the pivot 26. The cable stress therefor equals the load 78 and divided by 64, or 1.22xload.

At the same time, the resultant of the forces lies 5 mm. beyond pivot 26, and on that side of the pivot 26 tending to swing the boom 26 downwardly, thus eliminating the possibility of a flying boom.

When the boom is in its upper position illustrated in full lines in Fig. '1, the resultant will lie on the left side of the pivot 26, but since this pivot is no longer functioning because the boom 26 and the bearing member 2| move together about pivot 22, we still will not have a free swinging boom. The resultant will lie 5 mm beyond the pivot 22 of the bearing member 2i so that this resultant will lie in a position tending to swing the boom downwardly, thus eliminating the possibility of a flying boom.

With the construction of my invention, therefore, I have a relatively low stress in my cable at all times, that is, approximately 1.22 X load, while at the same time my boom is so positioned at all times that it cannot fly upwardly and out of control. I

In Fig. 8, I illustrate a boom 26 having but one pivot 22b and actuated by a cable drum 3| and a cable 29, as in the case of Fig. 7. In' Fig. 8, the boom is shown in a lowered dotted line position with the load endof the cable 86 mm. from the center of the mast, this being the same distance set forth in Fig. 7. In its raised full'line position, the boom 26 in Fig. 8 is in the same relative position that it is in the full line position of Fig. 7; that is, with the load side of the cable 50 mm. displaced from the center of mast l6. In its dotted. line position, the load is displaced 92 mm. from its pivot 22b, while the cable reel 3| is displaced 51 mm. from said pivot shaft 22b. Therefore, the cable stress in the downward position will be load x 92 divided by 51, or. 1.8 X load. The cable stress is therefore considerably greater than the cable stress in the construction of Fig. 7, which is the construction of my invention.

The resultant of the forces is displaced 28 mm. from pivot 22b in Fig. 8, thus making it'very difficult to control the lowering of the boom and also the raising of the boom.

With the boom in its full line position corresponding to the full line raised position of the boom in Fig. 7, the resultant will lie only 3.5 mm. beyond, the shaft 22b, and in this position will still prevent a flying of the boom. It will prevent a flying of the boom by a smaller margin than in Fig. 7, even though the incidental cable stresses are much greater than in Fig. 7. It will therefore be appreciated that with the conditions exactly the same, my invention will contribute a higher safety factor inso far as preventing a flying boom, while allowing for a very much lower I cable 'stress than in the conventional construction of Fig. 8.

In Fig. 9, I illustrate a possible modification in which a lower stress on the cable may be obtained, but in this modification, it is quite well illustrated that a flying boom will result. Thus, in Fig. 9, when the boom is in its lowered position with the load end of the cable displaced 86 mm. from the mast center, the resultant of the forces lies on the proper side of the pivot 22c. In this condition of the parts, the cable stress is exactly the same as it is in Fig. 7. However, when the boom is raised to its fully elevated position corresponding to the fully elevated position of Fig. 7, the resultant of the forces lies on the left side of the pivot 220 with the result that the boom will fly upwardly and will be positioned so that it cannot possibly be lowered except by a resetting of the parts, possible only through a considerable amount of work, and the use of additional power mechanisms. I

I believe that through the diagrams of Figs. 7, 8 and 9, ,I have amply illustrated how my invention contributes to the art a boom mounting in which the boom may be raised together with its load, and with a very low incidental cable stress,

while at the same time, the resultant of the forces set up will lie on that side of the pivot of the boom which will prevent a free flying of the boom. Incidentally, it should be explained that while in Fig. 7, the hook and boom are shown in an average raised hook position, Fig. 8 shows the hook raised to its highest position, while Fig. 9 shows the hook in its lowest position which it may maintain together with the boom. Further lowering of the hook in Fig. 9 will be relatively to a stationary boom as in Fig. 11

It should be appreciated, of course, that while I have illustratedone modification of my invention, it will be possible for 'those skilled in the art to devise other modifications embodying the principle of my invention while utilizing other specific mechanisms. Therefore, I feel myself entitled to claims of relatively broad scope.

I claim:

1. In a device of the class described, a pivoting boom, a pivoted bearing member, means whereby said boom is pivotally supported on said bearing member for pivoting movement relatively thereto, a cable for moving said boom from a position substantially at anangle to the vertical to a position less angular relatively to the vertical, and automatically acting means whereby during at least part of said movement said boom and bearing member are moved together about the pivot of said bearing member, the pivot of said boom on said bearing member being so related to the pivot of said bearing member, and to said automatically acting means, that said automatically acting means will act to move said boom and bearing member together about the pivot of said bearing memberjust prior to the point where the resultant of the forces, including said cable force, about said boom would fall at a point on the side of said boom pivot causing a free upward swinging of said boom, whereby the said resultant always falls on that side of the pivot then functioning so that its effect will be to swing the boom downwardly.

2. In a device of the class described, a pivoting boom, means supporting said boom for automatic pivotal movement on successive pivots, a cable for swinging said boom on said successive pivots through a continuous reeling in thereof, a load sheave at the end of the boom over which the cable reels, a load hook supported by that portion of the cable overhanging said sheave, the spacing and order of the successive pivots on which said boom swings being so determined relatively to the resultant of the forces of said cable pull on the one side, and the weight of the load and boom on the other side, that said resultant of the forces will lie on a side of the particular pivot then functioning, whereby its efiect will be to swing the boom downwardly.

3. In a device of the class described, a pivoting boom, a bearing member for said boom, a pivot on which said bearing member pivots, means supporting said boom for pivotal movement on and relatively to said bearing member, a single means for swinging said boom on its pivot relatively to said bearing member, and means automatically eiTective after a predetermined amount of movement of said boom on said bearing member whereby said single means swings said boom and bearing member together about the pivot of said bearing member, substantially for the purpose described. v

4. In a device of the class described, a pivoting boom, a bearing member for said boom, a pivot on which said bearing member pivots, means supporting said boom for pivotal movement on and relatively to said bearing member, a single means for first swinging said boom on its pivot relatively to said bearing member and then together with said bearing member about the bearing member pivot, and automatically acting means for connecting saidbearing member and boom for/swinging together on the pivot of said bearing'member, the pivot of said boom on. said 10 bearing member being so related to the pivot of said bearing member, and to said automatically acting means, that said automatically acting means will act to move said boom and bearing member together about the pivot of said bearing 15 member Just prior to the point where the resultant oi the forces, including said single means, about said boom would fall at a point on the side of said boom pivot causing a free upward swinging of said boom, whereby the said resultant aiways falls on that side of the pivot then functioning so that its effect will be to swing the boom downwardly.

5. In a device of the class described, a pivoting boom, a bearing member for said boom, a pivot as on which said bearing member pivots, means supporting said boom for pivotal movement on and relatively to said bearing member, a cable for swinging said boom on its pivot relatively to said bearing member from a position substan- Sii tially angular relatively to the vertical to a second position less angular relatively to the vertical, and automatically acting means connecting said boom and its bearing member at said second position whereby said boom and its bearing 5 member thereafter swing together about the pivot of said bearing member, the pivot of said boom on said bearing member being so related to the pivot of said bearing member, and to said automatically acting means, that said automati- (l cally acting means will act to move said boom and bearing member together about the pivot of said bearing member just prior to the point where the resultant of the forces, including said cable force, about said boom would fall at a I point on the side of said boom pivot causing a free upward swinging of said boom, whereby the said resultant always falls on that side of the pivot then functioning so that its effect will be to swing the boom downwardly.

6. In a device of the class described, a boom, a bearing member, a pivot on which said bearing member is supported for pivoting movement, a pivotal support for said boom on said bearing member, stop means, on said bearing member contacted by said boom when said boom is moved to a predetermined angular position, power means for swinging said boom upwardly, said power means swinging said boom about its pivot on ,said bearing member from a lower position to said predetermined angular position, continued application of said powermeans acting through said stop means to swing said bearing member and boom together on the pivot support of said boom, the pivot of said boom on said bearing member being so related to the pivot of said bearing member, and to said stop means, that said stop means will act to move said boom and bearing member together about the pivot of said 7 bearing member just prior to the point where the resultant of the forces, including said power means, about said boom would fall at a point on the side of said boom pivot causing a free upward swinging of said boom, whereby the said u resultant always falls on that side of the pivot area-roe then functioning so that its effect will be to swing the boom downwardly.

7. -In the combination of claim 3, a load cable as the single means for swinging the boom or the boom and bearing member together, a load I sheave at'the end of the boom over which the cable reels, a load hook supported by that portion of the cable overhanging said sheave, the pivots on which said boom, or said boom together with said bearing member swing, being so posll0 tioned relatively to the resultant of the forces of said cable pull on the one side, and the weight of the load and boom on the other side, that said resultant of the forces will lie on a side of the particular pivot then functioning, whereby its 15 eifect will be to swing the boom downwardly.

8. In the combination of claim 4, a load cable as the single means for swinging the boom or the boom :and bearing member together, a load sheave at the end of the boom over which the a cable reels, a load hook supported by that portion of the cable overhanging said sheave, the pivots on which said boom, or said boom together with said bearing member swing, being so positioned relatively to the resultant of the forces of said cable pull on the one side, and the weight of the load and boom on the other side, that said resultant of the forces will lie on a side of the particular pivot then functioning, whereby its effect will be to swing the boom downwardly.

9. In a device of the class described, a pivoting boom, a bearing member for said boom, a pivot on which said bearing member pivots, means supporting said boom for pivotal movement on and relatively to said bearing member, a cable for first swinging said boom on its pivot relatively to said bearing member and then together with said bearing member about the bearing member pivot, automatically acting means for connecting said boom and said bearing member for a swinging together on said bearing member pivot,

a load sheave at the end of the boom over which the cable reels, a load hook supported by that portion of the cable overhanging said sheave, the pivots on which said boom swings alone, or on a which said boomand said bearing member swing together when connected, being so positioned relatively to the resultant of the forces of said cable pull on the one side, and the weight of the load and boom on the other side, that said resultant of the forces will always lie on a side of the particular pivot then functioning, whereby its effect will be to swing the boom downwardly.

10. In a device of the class described, a tilting boom, a bearing member, a pivot support for said I boom on said bearing member, a pivot support for said bearing member, a sheave at the end of the boom, a load cable running over said sheave and adapted to lift a load suspended therefrom and also to swing said boom upwardly on its piv- U ot relatively to said bearing member, and stop means between'said boom and bearing member whereby after said boom is moved on its pivot to a particular position with relation to said bearing member it thereafter automatically moves integrally with said bearing member about the pivot of said bearing member, the pivot of said boom on said bearing member being so related to the pivot of said bearing member, and to said stop means, that said stop means will act to move said boom and bearing member-together about the pivot of said bearing member just prior to the point where the resultant of the forces, including said cable force, about said boom would fall at a point on the side of said boom pivot causing a TI boom, a bearing member, a pivot support for free upward swinging of said boom, whereby the said resultant always falls on that side of the pivot then functioning so that its effect will be to swing the boom downwardly.

11. In a device of the class described, a tilting said boom on said bearing member, a pivot support for said bearing member, a sheave at the end of the boom, 9. load cable running over said sheave and adapted to lift a load suspended therefrom and also to swing said boom upwardly I on its pivot relatively to said bearing member,

stop means between said boom and bearing member whereby after said boom is swung upwardly to a particular position with relation to said hearing member it thereafter automatically swings integrally with said bearing member about the pivot of said bearing member, the particular one of said pivots about which said boom swings alone, or on which said boom swings together with said bearing member, being so positioned relatively to the resultant of the forces of said cable pull on one side, and the weight of the load and boom on the other side, that the said resultant of the forces will lie on that side of the particularpivot then functioning, whereby its effect will be to swing the boom downwardly, the

extreme upward position of said boom being so related to its pivot on said bearing member that said resultant of forces would cause a free upwardly swinging boom were said boom movable on said pivot when in said upward position.

CHARLES s. 'SCHROEDER. 

